The present invention relates to a transmission device and transmission method particularly suited for application in, for example, an audio visual server system.
Conventionally, audio signal coding devices where baseband audio signals comprising inputted analog waveforms are sampled at a number of defined sampling frequencies, code processed and then outputted have been widely used.
On the other hand, there are currently various types of coding devices for coding image signals, but recently, image coding devices represented by using the MPEG method have come to be in general use.
One of the characteristics of MPEG-defined image coding is that variable-speed playback of the image at the time of decoding is possible.
However, with usual MPEG method encoding devices, the image signal and accompanying audio signal are independently encoded and the encoding of the image signal takes into consideration the aforementioned variable-speed play-back. However, the encoding of the audio signal does not take into consideration this variable-speed playback and the played-back audio signal is therefore silenced at the time of variable-speed playing-back of the image signal. Generally, encoding taking this kind of variable-speed playback into consideration has been difficult with the existing MPEG method audio encoding devices.
Therefore, with MPEG method encoding devices, with regards to the image signal, if the audio signal that accompanies this image signal can also be encoded so as to be played-back at a variable speed in synchronism with the variable-speed playback of the image signal, then the aforementioned kind of silencing of the audio signal can be avoided even during a specific playing-back and the audio signal can be perceived as being information that is in synchronism with the image signal.
Further, the number of decoding devices produced is definitely greater than that of encoding devices and decoding devices have become particularly superior ones both in economical efficiency and maintainability. Therefore, for example, in a system where a plurality of decoding devices are connected to a single encoding device, it is much disadvantageous for the decoding device to have a special function such as the variable-speed playback of an audio signal in simplifying and downsizing the structure of the decoding device.
It is therefore an object of the present invention to provide a transmission device and transmission method which are flexible and expandable.